Global Long-Term Soil Moisture Retrieval Combining Fengyun-3B and Fengyun-3D Microwave Radiometers

doi:10.11871/jfdc.issn.2096-742X.2026.05.002

Abstract

Abstract:

[Objective] To address the long-term soil moisture continuity problem caused by systematic differences between Fengyun-3 (FY-3) B and D satellites, this study develops a cross-satellite consistent global soil moisture dataset. [Methods] A long short-term memory (LSTM) retrieval method based on microwave emissivity features is proposed. Multi-frequency dual-polarization emissivity time series are used as inputs, and MCCA SMAP soil moisture is used as the training target. Separate retrieval models are established for FY-3B and FY-3D to generate a global daily soil moisture product at 25 km resolution for 2012-2025. [Results] Ground-network validation shows good agreement between the retrieved product and in situ soil moisture observations from the Naqu and Wudaoliang networks on the Tibetan Plateau, with correlation coefficients (R) exceeding 0.91 and unbiased root mean square errors (ubRMSE) below 0.039 m³/m³. [Limitations] Due to the limited availability of in situ observations, product uncertainties over dense forested areas require further assessment using additional in situ measurements. [Conclusions] Compared with the FY-3 Level-2 (L2) soil moisture products, this study improves the consistency and stability of FY-3B/3D retrievals and provides data support for long-term hydrological monitoring using domestic satellites.

Key words: remote sensing, soil moisture, Fengyun-3 (FY-3), Long Short-Term Memory network (LSTM), long time series data

JING Runsheng, BAI Yu, CAO Yipeng, ZHANG Haojie, DUAN Pan, ZHAO Tianjie, XUE Huazhu, ZHENG Donghai, XU Ronghan. Global Long-Term Soil Moisture Retrieval Combining Fengyun-3B and Fengyun-3D Microwave Radiometers[J]. Frontiers of Data and Computing, 2026, 8(5): 18-33, https://cstr.cn/32002.14.jfdc.CN10-1649/TP.2026.05.002.

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参数	10.65 GHz （X）	18.7 GHz （K）	23.8 GHz （K）	36.5 GHz （Ka）	89.0 GHz （W）
极化方式	H/V	H/V	H/V	H/V	H/V
空间分辨率（km）	51×85	30×50	27×45	18×30	9×15
入射角	约53°	约53°	约53°	约53°	约53°
幅宽（km）	1,400
过境时间（地方时）	FY-3B：升轨约13:40，降轨约01:40 FY-3D：升轨约14:00，降轨约02:00

观测网络名称	选取数据时间	测量深度	传感器数量
Naqu（那曲，中国）	2014.03~2021.09	0~5 cm	73
SMN-WDL （五道梁，中国）	2019.09~2021.11	5 cm	10
AMMA-CATCH （尼日尔）	2012.01~2018.12	5 cm	7
REMEDHUS （西班牙）	2012.01~2022.12	0~5 cm	22
Oznet-Yanco （澳大利亚）	2012.01~2021.08	0~5 cm	19

卫星载荷	训练时段	评估时段	训练样本	独立评估样本数
FY-3B MWRI	2016-01-01至2018-12-31	2019-01-01至2019-08-19	降轨: 74,347,981 升轨: 76,144,331	降轨: 12,885,546 升轨: 13,363,921
FY-3D MWRI	2018-01-01至2020-12-31	2021-01-01至2021-12-31	降轨: 73,751,113 升轨: 75,680,673	降轨: 24,760,023 升轨: 25,490,764